1. Field of the Invention
The present invention relates to an anchoring element of a biocompatible material for implantation in the bone tissue of two bones or two portions of a bone separated by non-ossified tissue and, more particularly, to a doubly anchored dental fixture for replacement of one of several teeth in the upper jaw.
2. Description of the Related Art
Known anchoring elements or fixtures are of a generally cylindrical form and provided with outer threads. They are adapted to be screwed into holes drilled in the respective bone. In certain cases, particularly in cases where substantial bone resorption has occurred, the appropriate bone holding the anchoring element or fixture of a prosthesis may be too weak to bear the load of a prosthesis. In such case, the load might be reduced by multiple anchoring, for instance, by anchoring the fixture in two bones or two portions of the same bone.
An appropriate example of the above situation is a patient who has been edentulous for a long time. For this reason, the patient's jawbone has become partly resorbed and its retention capacity has become inadequate for the anchoring of one or several dental fixtures. Such a patient may not be successfully treated by implanting a desirable prosthetic appliance, or may not be willing to accept the substantial risk which accompanies dental surgery in such circumstances. The patient might lose the prosthesis or risk jawbone fracture.
U.S. Pat. No. 5,199,873 discloses a dental implant intended to be anchored completely in the jaw bone. The outside surface of the fixture is stepped downwardly by a plurality of steps, each of which is threaded. The implant is inserted in a corresponding stepped bore in the jawbone. Only the last stepped portion is screwed into the jawbone. Thus, the implant is not screwed into the jawbone over its entire length, of but only over a small length, significantly reducing trauma. However, the bore in the jaw must be provided with steps dimensioned similarly to the stepped portions of the implant, which requires a multi-step, difficult drilling process.